The invention relates to a device for galvanically coupled transmission of electrical signals. Devices of this kind are known as sideways or, in the case of twisting motion, as slide rings. The contact system consists primarily of metallic sideways, which are in galvanic contact with so-called brushes. Said brushes can be simple metal wires, woven metal, or sintered materials which as a rule contain electrical conducting and lubricated components. The brush type in each case is selected in accordance with the aim of the invention. Metal wire brushes, for instance, are generally very suitable for slow start-up speeds at low voltage levels. At higher voltage strength or at higher speeds, so-called carbons are generally used. Carbons as a rule consist of a sintering material containing graphite and conductive materials such as copper or silver. Other combinations, which are also common, contain Teflon as a sliding material.
In the following description, no distinction is made between contact carbons and brushes on the one hand, and carbon brushes on the other, since, in most technical jargon usage, these terms are interchangeable. In addition, the term xe2x80x9celectrode bagxe2x80x9d stands for a brush holder, which generally takes the form of a tube with a rectangular or square cross-section, and serves to conduct the carbon so that it can move along only one axis.
Metal wire brushes are particularly simple to secure in place, because at the current state of technology they can be soldered or pressed in without any problems into conductor plates. The holders for carbon brushes are as a rule basically more expensive, first, because they must be issued for higher voltage strengths and, second, because they are intended to allow a multi-axis stable conducting of the brush. One device, in which the carbon is secured in a mounting constructed on a plate, is described in European Patent Application EP 0928051 A2. Devices of this type are primarily designed for use in electrical engines. In this application, a relatively low number of carbons run on a commutator. If the carbons are worn out, it is a simple matter to exchange a few carbons individually. With top-of-the-line sliding contact devices, in which signals must be transmitted with high quality and where low contact noise is essential, a great many carbons are used in most cases. Thus a slide ring system may contain well in excess of 100 carbons. If such a high number of carbons must be individually exchanged and even contacted again, this would take considerable time.
It is therefore the task of the invention to present a device which, even with high numbers of carbons, allows for simple maintenance or a simple replacement of carbons.
The solution of this task is indicated in claim 1. Advantageous applications are indicated in the additional claims.
In accordance with the invention, several carbon holders are arranged on a common supporting plate. The supporting plate itself can be a mechanical stable plate of electrically conducting material, or else can consist of an insulating material with a device for electrical contact. The conductor plate along with the carbon holders affixed to it is arranged in such a way that it can be exchanged as a single complex. This reduces the cost of maintenance for devices with high carbon content.
In a particularly advantageous realization of the invention, the supporting plate takes the form of a conductor plate.
In an additional advantageous realization of the invention, at least one connection element that is electrically connected with the carbons or carbon holders is provided for contacting the single complex. This can take the form, for instance, of a plug contact or a screw clamp.
In a particularly advantageous realization of the invention, the carbon holders, which are assigned to the carbons for individual sideways or groups of sideways, are arranged collectively on individual conductor plates. In sliding contact arrangements, in which for example power or signals of small capacity are transmitted, the lifetimes of the carbons vary. In most cases the contact carbons used for power transmission have a substantially shorter lifetime and must therefore be replaced frequently. It is useful therefore to bring together the carbon holders of the carbons of individual sideways or individual groups of sideways on individual conductor plates.
In an additional advantageous realization of the invention, the conductor plate is arranged in such a way that it assumes the function of the mechanical guidance or of the electrical contacting of the carbons. As tests have shown, with silver graphite carbons with connection cords, which are inserted in an electrically conductive electrode bag, about one-third of the current flows through the connection cord, while the major portion of the current runs over the electrode bag. But if the conductor plate is set up so that it can come into mechanical or electrical contact with the carbon, then in this manner a considerable portion of the current can be transmitted.
In an additional advantageous realization of the invention, the conductor plate is so designed that, in the case of a carbon with connection cord, the conduction cord can be directly contacted with the conductor plate. Such an arrangement is particularly appropriate if no electrical contact can be produced between the carbon holder inner lining and the carbon.
In an additional advantageous realization of the invention, additional guide units of the sliding contacts are affixed on the conductor plate, which guide units for instance are designed as U-shaped so that they present a mechanical guidance of the slide carbons with the conductor plate.
In an additional advantageous realization of the invention, in the case of carbons with at least one lateral guide surface, they are arranged so that this guide surface stands in contact with an electrical conductive surface of the conductor plate. With square-shaped carbons this means that, for instance, a lateral surface is arranged parallel to the conductor plate on a conducting track, which serves the electrical contact.
In an additional advantageous realization of the invention, individual conductor plates are secured in their position through mechanical guide elements. Particularly suitable for this are guide tracks and/or alignment pins which make possible a mounting without additional adjustment efforts.
In an additional advantageous realization of the invention, individual conductor plates are secured in their position by means of a notching device or other mechanical locking system. Particularly advantageous here are notching devices that can be released only by means of a tool, such as for instance a screwdriver. For an additional security element, a securing screw can be provided to prevent any accidental release of the conductor plate from its holder.
In an additional advantageous realization of the invention, the conductor plates are arranged so that individual conductor plates or groups of conductor plates can be exchanged to replace worn-out contacts.
In an additional advantageous realization of the invention, at least one sliding contact has a marker to provide a measurement of abrasion. As a result, the wearing out of the sliding contact can be indicated. In one group of parallel connected sliding contacts, they generally show a similar rate of wear. It is sufficient, therefore, to monitor the wearing of just one sliding contact.
In another realization, at least one sliding contact is connected with a mechanical wear indicator. Such a wear indicator can be a simple pin, which indicates the remaining level of the sliding contacts, or else a complex mechanical structure with tracer levers or the like.
In an additional advantageous realization of the invention, electronic components are integrated on the conductor plate to diagnose or signal the condition of the sliding contact arrangement. These electronic components can communicate the condition of the sliding contact device by means of numerous measurements, such as of the carbon route, of the wear, or of the electrical transmission resistance, and relay this condition to a central monitoring unit. This unit is then in a position to give a signal in a timely manner for the replacement of the contact carbons or of individual conductor plates.
The invention is described below without limitation of the general inventive concept on the basis of realizations as per illustrations, to which explicit reference is made to communicate all details of the invention that are not further elaborated in the text. The illustrations are as follows.